Field of the Invention
The present invention relates to an optical apparatus, a processing apparatus, and an article manufacturing method.
Description of the Related Art
For example, Japanese Patent No. 4386137 and Japanese Patent Laid-Open No. 2011-121119 disclose light beam parallel shift mechanisms in a conventional laser processing apparatus. In Japanese Patent No. 4386137, a light beam is parallelly shifted by rotating a transparent member. In Japanese Patent Laid-Open No. 2011-121119, a light beam is parallelly shifted using two synchronized angle changing mirrors.
In the light beam parallel shift mechanism of Japanese Patent No. 4386137, however, since the parallel shift amount of the light beam is determined by the rotation angle and the length of the transparent member, the inertia in rotation becomes large, and it is therefore difficult to do desired light beam shift at a high speed. For example, assume a case in which a light beam parallel shift amount of 5.3 mm is attained by a rotation angle of ±10° of a transparent member (quartz glass n=1.45) by the method of Japanese Patent No. 4386137. In this case, the size of the transparent member is realistically designed to about 95 mm×16 mm×13 mm. As a result, the inertia is as large as 33,000 g·mm2, and it is difficult to perform parallel shift at a high speed.
The technique of Japanese Patent Laid-Open No. 2011-121119 solves the problem of the large inertia of the rotating member. However, since it is difficult to accurately synchronize the two mirror rotation mechanisms in a high-speed operation, the angle of the exit light beam is not constant, and it is difficult to parallelly shift the light beam.